1. Field of Invention
This invention relates to sealing rings having a coating of wear resistant material deposited on the bearing face thereof and more particularly to a piston ring having a chrome-filled stepped groove in its outer bearing face.
2. Description of the Prior Art
Chromium plated piston rings are old and well known in the art. However, the use of such rings has not been without problems. A major problem is the tendency of the chromium layer to crack from fatigue and cause the ring body to break in fatigue. Various approaches have been taken to eliminate this problem. Generally to prevent the breakage the industry has gone to higher strength base materials. Even in view of the added cost, the substitution has not been entirely successful.
Such rings have been successful in conventional diesel engines. However, the operating conditions imposed by the new high speed and high powered diesel engines have been such as to still cause ring failure, even within the warranty period. In one of these engines, the stresses included on the compression rings caused such a high rate of fatigue failures that continued production of the engine was questionable.
Accordingly, it is an object of the present invention to provide a chromium plated piston ring which is not subject to failure by reason of the fatigue of the ring and, therefore, is able to withstand the stresses imposed on compression rings by high speed and high powered diesel engines.